I think now is the perfect time to prune. Wait until your roses begin to show some signs of waking up from their dormant period. Just watch for swellings on the canes indicating new leaves are about to emerge. Then prune everything down to 15-18". Remove any obviously diseased or dead canes, and any old non-productive canes. Save 3-5 of the healthiest canes and remove all others. The ideal result is a V-shape with a relatively open center. If any suckers are growing from below the grafted part of the rose, pull them off with a downward motion, to help remove any growth buds that might result in additional sucker growth. Finally, cut the remaining canes to an outward facing bud in the direction you want the growth to take. It's okay to leave the last of the season's flowers on the bush. They develop into rose hips and when that happens it signals the plant to stop growing at to prepare for winter. Hope this answers all your questions!